(1) Field of the Invention
The present invention relates to vehicle location detection devices which specify, using a vehicle sound of another vehicle, a location of the other vehicle, and in particular to a vehicle location detection device which specifies a location of the other vehicle hidden behind an obstacle.
(2) Description of the Related Art
When a vehicle is in operation, detecting other vehicles near or approaching the vehicle is useful for safe driving. Various methods have been conventionally proposed as techniques for detecting such vehicles.
For instance, there is a technique for detecting a sound pressure and a frequency of a sound emitted by a moving object and specifying a distance to the moving object based on the detected sound pressure and frequency (e.g., Patent Reference 1: Japanese Unexamined Patent Application Publication No. 1-265176). In Patent Reference 1, the distance to the moving object is determined by calculating, using a distance attenuation equation based on a sound pressure and a frequency, four variables which are sound pressures T1 and T2 (two variables), of a sound emitted by the moving object, at a sound source location of frequencies f1 and f2 and distances r1 and r2 (two variables) to two detection locations.
Furthermore, as another conventional technique, there is a technique for specifying a location of an emergency vehicle by detecting a sound pressure and a frequency of a warning sound emitted by the emergency vehicle, calculating a distance to and a moving direction of the emergency vehicle, respectively, based on the detected sound pressure and frequency, and referring to map information (e.g., Patent Reference 2: Japanese Unexamined Patent Application Publication No. 2005-301751).